In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here report an experimental study of droplet formation in a microfluidic cross ... [more ▼]

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here report an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the squeezing regime, which is composed of two distinct steps : filling and pinching. The duration of each step (and corresponding volumes of each liquid phase) are analyzed. They vary according to both water and oil flow rates. These variations provide several insights about the fluid flows in both phases. We propose several scaling laws to relate the droplet volume and frequency to the flow rate of both phases. We also discuss the influence of surfactant and channel compliance on droplet formation. [less ▲]

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here report an experimental study of droplet formation in a microfluidic cross ... [more ▼]

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here report an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the squeezing regime, which is com- posed of two distinct steps : filling and pinching. The duration of each step (and corresponding volumes of each liquid phase) are analyzed. They vary according to both water and oil flow rates. These variations provide several insights about the fluid flows in both phases. We propose several scaling laws to relate the droplet volume and frequency to the flow rate of both phases. We also discuss the influence of surfactant and channel compliance on droplet formation. [less ▲]

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here present an experimental study of droplet formation in a microfluidic cross ... [more ▼]

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here present an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the dripping regime. The dynamics of droplet formation is composed of two distinct steps : filling and pinching. The duration of each step (and cor- responding volumes of each phase) are analyzed. They vary according to both water and oil flow rates. These variations reveal several insights about the fluid flows in both phases. We propose some scaling laws to relate the droplet volume and frequency to the flow rate of both phases. We also discuss the influence of surfactant on droplet formation. [less ▲]

In microfluidics flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. Nevertheless, the scaling laws associated to droplet length, speed and frequency could ... [more ▼]

In microfluidics flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. Nevertheless, the scaling laws associated to droplet length, speed and frequency could not be identified yet, owing to the large number of parameters involved (incl. complex geometry). We here present an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the dripping regime. The formation sequence is decomposed in two steps, inflation and squeezing, that vary differently according to both water and oil flow rates. These variations reveal several insights about the fluid flows in both phases. From there we infer the scaling law that relates droplet volume and frequency to the Capillary number associated to each inlet flow rate. This law involves a minimum of fitting parameters. We finally discuss the influence of inlet control (flow rate vs. pressure) and surfactants on the formation dynamics. [less ▲]

In microfluidics flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. Nevertheless, the scaling laws associated to droplet length, speed and frequency could ... [more ▼]

In microfluidics flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. Nevertheless, the scaling laws associated to droplet length, speed and frequency could not be identified yet, owing to the large number of parameters involved (incl. complex geometry). We here present an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the dripping regime. The formation sequence is decomposed in two steps, inflation and squeezing, that vary differently according to both water and oil flow rates. These variations reveal several insights about the fluid flows in both phases. From there we infer the scaling law that relates droplet volume and frequency to the Capillary number associated to each inlet flow rate. This law involves a minimum of fitting parameters. We finally discuss the influence of inlet control (flow rate vs. pressure) and surfactants on the formation dynamics. [less ▲]

In droplet microfluidics, the pairing of droplets in parallel channels is sometimes required, e.g. to control their encounter and to promote their coalescence. Prakash and Gershenfeld [1] showed that ... [more ▼]

In droplet microfluidics, the pairing of droplets in parallel channels is sometimes required, e.g. to control their encounter and to promote their coalescence. Prakash and Gershenfeld [1] showed that passive synchronization could be achieved with bubbles in a ladder-like channel network. Bubbles flow in the rails and induce recirculation in the interconnecting rungs, which supposedly provides the feedback and subsequent synchronization. Ahn et al. recently extended this study to trains of droplets in flow-rate-driven conditions [2]. We here present an extensive experimental and theoretical investigation of droplets synchonization in multiple parallel channels. Droplets are produced with independent flow-focusing structures. Several experimental conditions are tested, including several geometries (and subsequent flow resistance) and inlet conditions (pressure-driven vs. flow-rate-driven). An extension to three rails is also considered. The microfluidic chips are designed with the help of a lumped-element model in which droplets are driven by the flows. [1] M. Prakash and N. Gershenfeld, Science 2007, 315, 832-835 [2] Ahn et al., Lab-on-a-chip, 2011, 11, 3956-3962 [less ▲]

We developed a microfluidic device for the detection of bio-molecules. The active part of the device is a biofunctionalized interdigitated capacitive sensor. The microsystem consists of a sensor on ... [more ▼]

We developed a microfluidic device for the detection of bio-molecules. The active part of the device is a biofunctionalized interdigitated capacitive sensor. The microsystem consists of a sensor on silicon chip, a microfluidic channel formed by photo-patternable resist and a plastic cover. We implemented a low temperature packaging process to assemble the sensor and prevent the biological material from degradation. [less ▲]

Influenza A viruses cause annual epidemics and occasional pandemics that spread worldwide. The nucleoprotein is essential for the survival of this virus and is thus well-conserved. We developed a ... [more ▼]

Influenza A viruses cause annual epidemics and occasional pandemics that spread worldwide. The nucleoprotein is essential for the survival of this virus and is thus well-conserved. We developed a quantitative electronic biosensor displaying a protein recognition thanks to the covalent grafting of anti-nucleoprotein antibodies. The detection device lies on interdigitated array microelectrodes (IDAM), covered with alumina (Al2O3) to protect the underlying aluminum and enhance the electrical coupling. As the dimensions of the IDAM can determine the sensitivity of the sensor, we processed 4 structures with varying electrode widths and spacings in the same silicon chip and assessed their individual performance. The sensing area of each sensor is 200*200 µm2 and the overall chip-size is 3*3 mm2. The sensor is mounted in a DIL-16-package partially encapsulated by resin. [less ▲]

We developed a method of assembly for electrical micro-bio-sensor. The system is a part of a micro-fluidic device based on a capacitive biosensor. The bio-sensor is designed for bio-molecules ... [more ▼]

We developed a method of assembly for electrical micro-bio-sensor. The system is a part of a micro-fluidic device based on a capacitive biosensor. The bio-sensor is designed for bio-molecules (specifically DNA and protein) detection, quantification and recognition. Using the developed method we assembled series of fully functional demonstrators. [less ▲]